Preparatory Study for the Synthesis of the Starfish Alkaloid Imbricatine. Syntheses of 5-Arylthio-3-methyl-L-histidines.
作者:Masashi OHBA、Takafumi MUKAIHIRA、Tozo FUJII
DOI:10.1248/cpb.42.1784
日期:——
Chiral syntheses of 3-methyl-5-(phenylthio)-L-histidine (8a) and 3-methyl-5-(1-naphthalenylthio)-L-histidine (8b), selected as models for the asteroid alkaloid imbricatine (7), have been accomplished through a 10-step route starting from 4(5)-bromoimidazole (9). The key steps involved were methylation of 9, hydroxymethylation of 4-bromo-1-methyl-1H-imidazole (11), replacement of the 4-bromo group by an arylthio group in the aldehyde 14, and introduction of a chiral α-amino acid moiety into the chlorides 17a and 17b by the "bis-lactim ether" method. The synthesis of the 4-(4-methoxybenzyl)thio analogue 17c, carried out in a similar manner, concluded formal syntheses of ovothiols A and C (1 and 3).